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Topic 7: Mechanisms of Microevolution

Terms in this set (17)

Mutations
the ultimate source of all variation
Produce new alleles
Randomly occurring events at low frequency
Natural selection
a form of selection in which individuals with favorable phenotypes survive to reproduce more than individuals with different phenotypes
Adaptive evolution
better match of organism and environment
Non-random mating
mechanisms where individuals are more likely to mate with individuals that possess a specific phenotype
Assortative mating (non-random mating)
individuals more likely to mate with similar (positive) or dissimilar (negative)
Mate selected for a single trait or a group of traits
Pairs share more (or fewer) traits than expected at random
Inbreeding (non-random mating)
mating of two genetically similar relatives
Increases homozygosity (decreases heterozygosity)
Inbreeding depression
reduction in fitness due to inbreeding
Self-fertilization (non-random mating)
Special form of inbreeding; Decreases heterozygosity; Still sexual reproduction (meiosis with fertilization); Does not necessarily produce identical offspring identical to parents
Gene flow
the transfer of traits in or out of a population
Immigration
Traits (alleles) move into the population from elsewhere
Often increases trait diversity in the population
Emmigration
Traits (alleles) move out of a population to elsewhere
Often decreases trait diversity
Genetic drift
any change in allele, or genotype, frequencies in a population that is due to chance (random events)
Fixation
when there is only one allele for a gene locus
Extinction
when a previous allele for a gene locus is lost
Alleles in smaller populations
Generally go to fixation or be lost much more quickly due to drift than in large populations
Bottleneck effect
sudden change in environment drastically reduces size of population; Surviving alleles result of chance alone
Founder effect
few individuals become isolated from larger population, smaller group establishes new population
Gene pool of new population differs from source population
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